#include<bits/stdc++.h> using namespace std; int main() { int n; cin >> n; int a[n][n]; for (int i = 0; i < n; i++) { for (int j = 0; j < n; j++) { cin >> a[i][j]; } } int sum = 0; for (int i = 0; i < n; i++) { for (int j = n - 1; j >= 0; j--) { if (i == j || i + j == n - 1) { sum = sum + a[i][j]; } } } cout << sum; return 0; }